Claudia Niewersch, S. Petzet, J. Henkel, Thomas Wintgens, Thomas Melin, P. Cornel:
Phosphorus recovery from eluated sewage sludge ashes by nanofiltration
In: Internaional Conference on Nutrient Recovery from Wastewater Streams, Vancouver, Canada, 10-13.05.2009
A combined process for a phosphorus recovery from sewage sludge ash was studied. The process consists of an acidic elution, ultrafiltration for the separation of particles, nanofiltration for the separation of phosphorus and neutralisation of the nanofiltration permeate. Filtration experiments were conducted with the nanofiltration polyamide membrane DL (GE Osmonics) with eluates of three different sewage sludge ashes and two different dilution rates as well as ultrafiltration experiments with polymeric membranes (UP150 by Microdyn Nadir) and ceramic membranes (UF50n by Atech). It was shown that the selectivity of the nanofiltration membrane depended significantly on the dilution rate of the ash elution. With the help of model solution experiments, a dependency of the phosphorus retention on the concentration of multivalent cations in the feed could be demonstrated. The performance of the ultrafiltration turned out to be relatively high (220 L/m2*h) and stable, also with an increasing concentration. In a preliminary economical analysis, the main cost factors were estimated for two different dilution rates and the three different ashes.